TEHRAN, Iran – Tens of thousands of Iranians chanted "Down with America" and "Death to Israel" during annual pro-Palestinian rallies nationwide on Friday, as a top leader said the U.S. would be making a "strategic mistake" if it pulled out of ongoing negotiations on Tehran's nuclear program.

The "Al-Quds Day" rallies took place as Iran and six world powers were meeting in Vienna to work out a deal to limit Iran's nuclear program in exchange for easing tens of billions of dollars in economic penalties on the Islamic Republic.

Iranian President Hassan Rouhani made a brief appearance at the rally in the capital, Tehran, but did not mention the nuclear talks that have blown past two extensions and entered the 14th day of the current round on Friday. U.S. Secretary of State John Kerry warned on Thursday that the Americans were ready to leave.

"If you drive the talks into a dead end then it will be you who will be committing a strategic mistake," Iran's parliament speaker Ali Larijani said at Friday prayers following the rally in Tehran, addressing the U.S. "And its outcome will not benefit you since Iran's nuclear staff are ready to accelerate nuclear technology at a higher speed than before."

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Iranian demonstrators burn a representation of the U.S. flag reading "down with America," in Arabic and Persian, during an annual pro-Palestinian rally marking Al-Quds (Jerusalem) Day at the Enqelab-e-Eslami (Islamic Revolution) St. in Tehran, Iran, Friday, July 10, 2015. Iran does not recognize Israel and since the 1979 Islamic Revolution has observed Al-Quds Day.(AP Photo/Vahid Salemi)
(The Associated Press)

At the rally, the hard-line protesters wrapped America, British, Israeli and Saudi flags around pillars and set them ablaze.

Since the 1979 Islamic Revolution, Iran has observed "Al-Quds Day" during the Islamic holy month of Ramadan. Tehran says the occasion is meant to express support for Palestinians and emphasize the importance of Jerusalem for Muslims.

Iran does not recognize Israel and supports anti-Israeli militant groups like Hamas in Palestine and Hezbollah in Lebanon.